The subject matter disclosed herein relates generally to appliances and, more particularly, to pump motors and control circuitry used to dispense a washing fluid throughout the appliance.
Pump systems in appliances such as dishwashers use different configurations of pump motors and control circuitry to dispense a washing fluid for cleaning objects (e.g., dishes and dishware). Many configurations utilize almost exclusively single-phase motors (e.g., asynchronous and synchronous motors) in connection with compatible control schemes. However, because these motors and control schemes are relatively simple and limited as to the tasks to be performed (i.e., dispensing the washing fluid), the appliance is provided with only a finite number and variations of operational cycles that define one or more spray properties (e.g., spray velocity). For effective cleaning of objects disposed in the dishwasher, these operational cycles typically require optimization of physical components of the dishwasher such as the spray arms and associated spray jets.
Limitations of single-phase motors often preclude their implementation in and use for design-related improvements such as those improvements that address demands for better wash performance, improved energy efficiency, and advanced features found in sophisticated appliances directed at “high end” markets. These limitations include inadequate speed control, low starting torques, and a lack of feedback as to the motor state (e.g., speed, torque, and power draw). Single-phase motors are also less efficient, as compared to other solutions, and such reduced efficiency can cause heat, which must be dissipated by fans, vents, or louvers such as in the motor compartment that houses the pump. Moreover, single-phase motors often exhibit vibration during operation, which can cause torque pulsations. These vibrations and/or torque pulsations are transmitted to the structure of the dishwasher and ultimately generate acoustical noise at levels that is difficult to control and not acceptable for consumer products such as household dishwashers.
Because of the perceived limitations with single-phase motors, other types of motors are often used to improve the performance of appliances. These motors include variable speed motors and, in particular, three-phase motors that require associated motor controllers. Such configurations overcome the limitations of single-phase motors but add cost and complexity.
Therefore there is a need for a solution that utilizes single-phase motors to achieve improved functionality of appliances.